1. Field of the Invention
The present invention relates in general to a fluid-filled cylindrical elastic mount which provides a vibration isolating effect based on flow of fluid contained therein, and more particularly to such an upper support which is capable of effectively isolating vibrations applied in the axial direction of the mount, and which is favorably used as an upper support in a suspension system of a motor vehicle, or a vehicle member mount, for example.
2. Discussion of the Prior Art
A so-called cylindrical elastic mount is known as one type of a mounting device which is interposed between two members of a vibration system for flexibly connecting the two members in a vibration-isolating fashion. This cylindrical elastic mount is constructed with an elastic or rubber body being formed between an inner metal sleeve, and an outer metal sleeve disposed radially outwardly of the inner sleeve with a suitable radial spacing therebetween. The elastic body elastically connects the inner and outer sleeves. The thus constructed elastic mount is adapted to mainly isolate input vibrations applied between the inner and outer sleeves in the axial direction of the mount. For example, the elastic mount of this type is widely used as an upper support in a suspension system, a strut bar cushion, or a member mount for a motor vehicle.
To meet increasing requirements for enhanced vibration isolating characteristics on recent high-grade cars, there has been proposed a fluid-filled cylindrical elastic mount having a fluid chamber which extends in the circumferential direction between the inner and outer sleeves, and which is filled with a non-compressible fluid. The elastic mount further includes a wing member which protrudes from one of the inner and outer sleeves toward the other in the fluid chamber, so as to substantially divide the fluid chamber into two sections. The wing member has a radial end face which cooperates with a radially opposed wall of the fluid chamber to define therebetween a restricted passage which communicates with the two sections.
Upon application of vibrations between the inner and outer sleeves in the axial direction of the mount, the wing member is axially displaced in the fluid chamber, causing the fluid to flow between the two sections through the restricted passage. Consequently, the fluid-filled cylindrical elastic mount provides an intended vibration isolating effect based on the fluid flow through the restricted passage.
In the fluid-filled cylindrical elastic mount, the fluid chamber is axially defined by respective elastic walls formed as part of the above-indicated elastic body connecting the inner and outer sleeves. Upon application of the vibrations between the inner and outer sleeves, the axially opposite elastic walls of the fluid chamber are strained and deformed by the inner or outer sleeve, in the same axial direction in which the wing member is displaced in the fluid chamber. Such deformation of the axially opposite walls of the fluid chamber results in reduction in the substantial amount of the axial displacement of the wing member in the fluid chamber, and resultant reduction in the amount of relative volumetric changes between the two sections of the chamber. Consequently, the amount of the fluid flowing through the restricted passage is reduced, resulting in deterioration of the vibration isolating effect of the mount based on the fluid flow through the restricted passage.